I left you off in my last
blog with some things to think about with brewing – primarily, what we like to
refer to as the six essential elements of brewing. If you haven’t read that blog, I suggest that
you read through briefly – because a lot of the science that I discussed there
will be relevant in the Cold Brew conversation.

At Stone Creek Coffee, we love
our Cold Brew. He even have it on tap at our Factory and Bay View stores. This special form of iced
coffee makes a sweet, rich, and fruity beverage. It also tends to not be bitter. However, if you think about brewing in
general, several elements of brewing are not necessarily “right” when doing
cold brew. For example, we use cold to
room temperature water to make cold brew.
But, to get the best extraction of coffee, you need to use 195-205F
water. Another element is brewing time:
most coffee brews quickly (2-5 minutes, depending on brew method). Cold brew often takes between 12-20 hours,
depending on method. However, it still
tastes good! What’s going on here?

Adjusting
the Brew Method

Brewing is all about
ratios and holding constant variables.
For example, I enjoy my drip coffee best at 2g per fluid ounce. I then find the grind that works with that
coffee at that ratio. I keep the temperature (195-205F) constant. I also look for a relatively stable time of
extraction. Those variables are tethered
to that ratio. When brewing hot coffee,
those variables are relatively static. When
we drop the temperature of the brew water over 130 degrees F, we need to make
some corresponding adjustments.

Have you ever brewed
coffee with water that was not quite hot enough? It probably tasted weak, yet not overtly bad. This is because the cooler water can dissolve
some of the coffee grounds, but not as much as hot water. If you measured the percentage solution, it
would be very, very weak (remember, ideal brew strength is between 1.15 and
1.35% solution). This tells us that we
have to compensate via grind or brew ratio somehow – and we need to make the
solution stronger. Fining the grind
could accomplish this, but due to the cold water, it wouldn’t necessarily make
a difference, since we can’t dissolve as much out. However, if you add extra coffee (we call
this updosing), you can actually dissolve more into the solution. When creating cold brew, you typically use a
much higher ratio of coffee to water (for the Mizudashi, 100g per 1L (3g:1oz
ratio) – for Toddy, 340g of coffee to 56oz of water (6g:1oz ratio).

Therefore, if we are using
more coffee, we have to keep a few other elements in mind. First, the coffee must become saturated with
water before it releases its flavor elements.
Agitation is imperative, especially when brewing large amounts of cold
brew. When creating this year’s cold
brew, it was randomly weak and watery. After
a lot of experimentation, I found out the cause of this was due to the grounds
not actually saturated. We can
accomplish this saturation easily if we use a coarser grind (less surface area
means that water can move evenly between the particles.) WE also want to make sure that we do not
over-extract the coffee as well – and the larger the particle, the longer it
will take to extract.

Science
of Cold Brew Extraction

Why is cold brew so
delicious? Above, I alluded to the fact
that coffee with cold water does not extract everything out of the grounds –
yet cold brew tastes like a “full” cup of coffee.

In the past, I’ve heard of
people enjoying cold brew because it was less acidic. To the contrary, citric (think citrus fruits)
and malic (think green apples and grapes) acids are fully extracted, even with
cool water. This is what contributes to
the fruity flavor of coffee – and arguably, what makes coffee so flavorful to
begin with. Sucrose is also extracted in
full proportions, which gives cold brew a rich sweetness. (Acid also increases the perceived sweetness
of coffee. Believe it or not, acid is
GOOD!)

So, what isn’t extracted
at this lower temperature? First, we see
lower amounts of chlorogenic acid, the most common acid found in coffee. Though we call it an acid, this is one of the
primary contributions towards making coffee bitter. Less chlorogenic acid = less bitter.

Interesting side note when
you don’t use enough coffee in your batch brewer, often this coffee tastes
bitter – this is due again to an increase in chlorogenic acid, which is one of
the elements extracted in higher concentration towards the end of a brew
cycle. If your coffee tastes bitter,
think about how we compensate with cold brew, and INCREASE the amount of coffee
grounds that you use.

Fatty acids are also not
extracted at a high concentration at colder temperatures. Bitter and salty flavors love fat (this is
why salt on French fries tastes so good).
When you remove the fat, the perception of the salty and bitter flavors
decrease. I am willing to wager that
your cold brew will never be bitter – it might be strong – but never bitter,
due to this fact.

How
to Brew

The other great thing about
cold brew is that you really don’t need a ton of equipment to make it. If you have a French Press at home, or even a
large plastic container (like this), you’re set. I’ve even heard of people using a coffee
filter, a mesh strainer, and a large bowl (similar to this).

Here’s my basic ratio for
cold brew:

Large vessel (like Toddy): 6g per 1oz
of water, use room temperature water, coarse grind, let steep for 12-15 hours. (This brew method makes a “concentrate” of
sorts – meaning, you can dilute if you choose).